As one of the prior art references relevant to the present invention, Patent Literature 1 (corresponding to International Application Publication No. WO2008/102458) is exemplified herein, which discloses ‘A condition of the ink droplets is represented by a black filled circle and a triangle in relation to the electrification waveform, in which the black filled circle represents charged ink droplets to be used for the printing and the triangle represents the non-charged ink droplets which are not used for the printing. The non-charged ink droplets have a role containing that it becomes a blank domain of the matrix character to be printed and it adjusts a time period between the longitudinal dot columns. In either case, the electric charge is not applied to the ink droplets such that the formed ink droplets are collected at the gutter 15 without jumping out them from the head. A slow speed printing condition shown in FIG. 14 and FIG. 15 indicates that the speed of traveling the printing object is relatively slow in comparison with time when the ink droplets ejected from the nozzle 11 are arranged on the printing object 19 in a predetermined number of pieces. For this reason, it is necessary to adjust time from printing termination of the preceding longitudinal dot column to printing start of the succeeding longitudinal dot column. The non-charged droplets of α pieces which are not printed are added, as a used amount, to the respective longitudinal dot columns of the matrix character containing four lines, each of which is made up of longitudinal Y dots which is a column of printed dots made up of the ink droplets of Y pieces. In the case of FIG. 15, the seven pieces of non-charged ink droplets, which are not printed out, are added to five pieces of the ink droplets to be used actually for the printing, which is handled as longitudinal dot columns, in relation to the matrix character made up of longitudinal five dots and transverse four lines’.